1. Field of the Invention
Embodiments of the invention relate to an apparatus and a method for polishing of substrates, and more particularly to a slurry dispenser and rinse arm and methods for thereof.
2. Description of the Related Art
Integrated circuits are typically formed on substrates by the deposition of conductive, semi-conductive, or insulative layers. After each layer is deposited, the layer is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the uppermost exposed surface of the substrate may become non-planar and requires planarization. This non-planar surface occurs when the thickness of the layers formed on the substrate varies across the substrate surface as a result of the nonuniform geometry of the circuits formed thereon. In applications having multiple patterned underlying layers, the height difference between the peaks and valleys becomes even more severe, and may be several microns.
Chemical mechanical polishing (CMP) is a planarization process which involves wetting a rotatable polishing pad with a chemical slurry containing abrasive components and mechanically polishing the front surface of the substrate against the wetted pad. The pad is mounted on a rotary platen and a rotatable substrate carrier is used to apply a downward pressure against the backside of the substrate. The polishing slurry is dispensed onto the pad through a slurry dispensing arm during polishing. The force between the carrier and the pad and their relative rotation, in combination with the mechanical and chemical effects of the slurry, serve to polish the substrate surface.
FIG. 1 depicts CMP system 10 in which a substrate 38 is held by a carrier head 46 which rotates about the central axis of the substrate 38. A circular polishing pad 40 is rotated while in contact with the bottom surface of the rotating substrate 38 being held by the carrier head 46. The rotating substrate 38 contacts the rotating polishing pad 40 in an area away from the center of the polishing pad 40. A slurry delivery arm 15 positioned above the surface of the polishing pad 40 dispenses a slurry 17, including, for example, an abrasive and at least one chemically-reactive agent, on the polishing pad 40 by way of a supply circuit 14 and 16. The slurry 17 is delivered to the center of the polishing pad 40 to chemically passivate or oxidize layers on the surface of the substrate being polished and abrasively remove or polish off select layers. A reactive agent in the slurry reacts with the film on the surface of the substrate to facilitate polishing. The interaction of the polishing pad, the abrasive particles, and the reactive agent with the surface of the substrate results in controlled polishing of the desired layers.
One problem encountered in CMP is that the slurry delivered to the polishing pad may coagulate, and along with the material being removed from the substrate, clog the grooves or other features on the pad thereby reducing the effectiveness of the subsequent polishing steps and increasing the likelihood of poor defect performance. Accordingly, rinse arms have been incorporated in some CMP systems to deliver water or rinse solutions to the pad to facilitate rinsing of the coagulated slurry and other materials from the grooves of the pad.
However, CMP systems encountered several drawbacks. First, the slurry delivery line often becomes clogged by condensed slurry inside the line. In addition, the rinse arm is usually in a fixed position over the pad therefore can only dispense to one location at a time. Still further, the rinse arm must be disposed over the center of the pad in order to deliver the rinse agent to that portion of the pad. Depending on the location of the substrate carrier head relative to the pad, rinsing of the central portion of the pad may not be accomplished unless the substrate carrier head is moved from the pad and polishing steps are discontinued.
Therefore, there exists a need to provide a slurry delivery and rinse system which is capable of self-cleaning, and which can adjustably deliver the slurry agent and rinse agent over the entire surface of the polishing pad without having to be located over the entire pad.